The present invention is directed to polyaxial bone anchors for use in spinal surgery and especially to such anchors that are in the form of a polyaxial bone screw adapted to receive a longitudinal connecting member and secure such a member to a vertebra.
Many spinal surgery procedures require securing various implants to bone and especially to vertebrae along the spine. For example, longitudinal connecting members such as elongate rods are often required that extend along the spine to provide support to vertebrae that have been damaged or weakened due to injury, disease or the like. Such rods must be supported by certain vertebra and support other vertebra. The most common mechanism for providing such structure is to implant bone screws into certain bones which then in turn support the rod or are supported by the rod. Bone screws of this type may have a fixed head or rod receiver relative to a shank thereof. In the fixed bone screws, the receiver cannot be moved relative to the shank and the rod or other longitudinal connecting member must be favorably positioned in order for it to be placed within the receiver. This is sometimes very difficult or impossible to do so polyaxial bone screws are commonly used. Polyaxial bone screws allow rotation of the head or receiver about the shank until a desired rotational position is achieved for the receiver relative to the shank after which the longitudinal connecting member can be inserted and the position of the receiver eventually locked with respect to movement relative to the shank.
The present invention is directed to such swivel head type bone screws and, in particular, to swivel head bone screws having an open head or receiver that allows placement of the longitudinal connecting member within the receiver and then subsequent closure by use of a closure top, plug or the like to capture the connector in the receiver of the screw.